Machine tool



Oct. 30, 1945. J. Bl. ARMITAG AL "2,387,820

MACHINE TOOL -Filed April 30, 1942* 10 Sheets-Sheet 1 W mw Oct. 30,1945. J. B. ARMITAGE ETAL 2,387,820

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J. B. ARMITAGE ETAL MCHINE TooL Filed April 50, 1942 10 Sheets-Sheet 9250 l I 13-15.. 2f

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' Oct. 30, 1945.

Filed April 30, 1942 J. B. ARMITAGE ETAL FE1@ T09JasEPH-HHmITHGBaHHIrM-BHRKEH- KUHTH-RIEDEL a fM/VLIHD- BUEHMER- EXT wwwv rection oi operation of the cutter spindle.

Patented Oct. 30,' 1945 UNITED STATES PATENT orf-'lcs Barker, Boehner,

Kui'tA.

Milwaukee,

Riedel, and Francis D.

Wis., assigner: to

Kearney & Trecker Corporation, West Allis, l Wis.,acorporation ofWisconsin A Application April 30, 1942, Serial No. 441,146

M Claims.

invention relates, generally, to machine tools and more particularly toimproved structural arrangements and novel driving and con- I trollingapparatus for a, machine tool such as a boring and threading' machine.

A general object of the present invention is to provide an improvedmachine tool especially adapted to perform boring or threadingoperations conveniently and with a high degree of precision. s l

Another object of the invention is to provide an improved boring andthreading machine arranged to cut-threads of either hand throughout awide range of pitches.

Another object of the invention is to provide improved mechanism foractuating and for controlling the movements of the operating elements ofa machine tool.

Another object is to provide a threading machine including depthmeasuring apparatus and control means associated therewith. for stoppingthe threading feed promptly upon arrival at a predetermined depth.

Another object is to provide an improved electrical control system for amachine tool.

Another object is to provide an improved electrical control system thatis especially arranged to condition a machine tool for performing eithera boring operation or a threading operation selectively.

A further object is to provide a thread cutting control includingadvancing and retracting feed According to this invention, a boring andthreading machinev is constituted by a base rpresenting a xed worksupporting surface and serving as a foundation' for a cooperatingspindle carrying upright slidably mounted forl movement along one sideof the work supporting surface. The upright carries a verticallyadjustable spindle head provided withv a ram in which a tool supportingspindle is rotatably mounted, the arrangement being suchl that thespindle may be moved to any position above or at the side of and belowthe work supporting surface. The spindle is driven by an electric motormounted on the' head and the ram is arranged to be driven in 50 feedingmovement in boring or threading operations by powerderivedy from' thespindle. The ram feeding mechanism includes reversing gearing, shiftablerange changing gearing, and lead v.als

for cutting either right or left hand threads of desired pitchthroughout a wide range. A forward feeding or threading operation. maybe terminated at any one ci several preselected positions 5 by means ofa multiple position stop mechanism arranged to disengage the ram feed oralternatively to actuate a limit switch which de-ener-I ram. Directionalcontrols for the ram may be conditioned by a selective switch to insurethe desired direction of ram feeding movement for either direction oispindle rotation. Other controis provide lfor rendering the forwardlimit switch and the brake inoperative selectively and for conditioningthe controls to effect inchins movements oi the ram by means of thedirectional controls. Separate motors vare provided for traversing theupright and for elevating the head by means of the usual screw and nutmechanisms. the screws in thisinstance being vdriven by worm wheels andcooperating worms. The two motors are directly connected to therespective worms that are also provided with-hand wheels for effectingmanual adjustments. Accurate positioning oi the upright is' accomplishedwith the aid oi measuring rods cooperating with a dial indicator, alimit switch being associated with the indicator for stopping thedriving motor when the upright arrives at a predetermined position.Further precise adjustment may then be eiected bythe hand wheel underguidance of the dial indicator. Other limit switches are provided tolimit movement of the upright in the other direction and to limit thevertical movements oi the spindle head.

The present invention is exemplified herein by means of an embodimentthereof in a boring and threading machine of the horizontal spindletype. However, it is to be understood that the particular mechanismherein set forth is intended to be illustrative only and that apparatusof difierent construction may be utilized in4 practicing the severalcharacteristics oi the invention within the range of equivalents oi thestructures dened `in the subjoined claims. The toregoing'and otherobjects of this invention, which will become more fully apparent from.`

the following detailed description, may bel achieved by the exemplifyingapparatus depicted in and further described in detail in connection withthe accompanying drawings. in which:

Figure 1 is a general view in front elevation of changing pick-oi!gearing arranged to provide 66 a horizontal boring and threading machineillusapply the brake at the retracted position oi the native of the typof machine tool in which the present invention may be incorporated toadvantage; Fig. -2 is a general plan view of the machine shown in Fig.1;

Fig. 3 is another general view of the machine, taken partly in endelevation and partly in vertical section along vthe lines 3-3 of Figs. 1and 2,

` with parts broken away to show the spindle support moving mechanism;

Fig. 4 is an enlarged detailed fragmentary view of the uprightpositioning mechanism, taken largely in vertical section along the lines4-.4 of

Figs. 1 and 2;

Fig. 5 is another fragmentary detailed view ofthe upright positioningmechanism, taken in vertical section along the lines 6-6 of Figs. 3 and4;

Fig. 6 is a view in vertical transverse section through the spindlecarrying ram structure and its driving mechanism, taken along the line6`6 0f Fig. 1:

' operating with it an Fig. 9 is a fragmentary view, partly in verticalsection through parts of the spindle head and ram,`shpwlng the ramfeeding and controlling mechanism, taken generally along the lines 3--9ofFigs.2and3; a Y v Fig. 10 is a detailed fragmentary view in transversevertical section through the spindle head and ram, taken along the lineI 0-i0 of Fig. 9;

Imovable supporting structure is such that a cutter carried bythespindle 26 may be moved in three mutually transverse planes. foruniversal adjustment relative to the work supporting surface 23.

As shown in Fig. Lthe spindle 28 may have cotlioard supporting structure29 that may be-` 'red on the work supporting surface 23 by means ofT-bolts 36 in position to support the outer end of .a cutter carryingarbor 3|, which is fitted in and has driving connection with the spindle26. The arbor 3 i, in turn,

servesv to support a cutter 32 for effecting a cutting operation upon awork piece 33 xed on the work receiving surface 23 by clamping r-bolts34 that cooperate with the T-slots 24.

As best shown in Fig. 3, the spindle carrying head 26 slides verticallyalong ways 35 at the front of the upright 22 and is counterbalanced bymeans of a counterweight 36 arranged for vertical movement within thehollow interior of the upright. The counterweight 'is connectedvto exertforce upward upon the head 26 by means of a pair of chains 31 whichoperate over idler sprocket wheels 38 carried in a bracket or cap 39secured to the top of the upright'22, the arrangement Fig. 11 is afragmentary view, partly in vertical section takenalong the lines I I-iI of Figs. 1 and 2. showing details of the adjustable outboard arborsupport; f

Fig. l2 is an enlarged view in end elevation of a cutter carryingattachment that is especially adapted when mounted on the ram of themachine, to operate-in a restricted space;

Fig. 13 is a view in longitudinal section through the attachment, takenalong the line i3-I3 of Fig. 12; and,

Fig. 14 is a schematic circuit diagram of the electrical control systemfor the actuating motors of the machine.

The particular exemplifying machine tool shown in the drawings as apreferred embodiment of the present invention is a special boring andthreading machine of the horizontal spindle type. although it is to beunderstood that various characteristics of the invention may be utilizedadvantageously in other machine tools of dill'erent construction.

Referring more specifically to the drawings and l particularly to Figs.1, 2 and 3 thereof showing generally the boring andthreadlng machine'described herein by wayof a complete disclosure of the invention, itwill be seen that the apparatus is constituted essentially by a` fixedbase or bed 2i with which is associated a relatively movable toolspindle supporting upright 22. As shown, the bed 2| is a rigid structureof hollow construction, presenting at' its top an elevated fixed workreceiving surface 23 tted with the usual spaced T-slots 24, and havingformedat one side of and below the levelv of the workfreceiving surfacean integral upright supporting surface or 'foundation 26. The upright 22likewise is of hollow construction and is slidablymounted on the surface26 for adjusting movement transversely of the work receiving surface 23.l A self-contained being such that the force exerted by the chains 31upon thehead'facilitate its adjustment along the upright.

Adjustment of the vertical position of the head 26 is eected by means ofan elevating screwf4l that is rotatably mounted in vertical position atthe front of the upright and that cooperates with a nut 42 fixed in thespindle head. Rotation of the elevati'ng screw 4I is effected by meansof a bevel gear 43 fixed on its lower end and disposed in mesh with asimilar bevel gear 44 that is rotatably mounted in a bracket 46depending from the upright 22. iAs shown in Fig. 5, the bevel gear 44has splined connection with a shaft 46 that is. journalled in the bed 2iin position parallel with the direction of movement of the upright 22,the arrangement being such that a driving connection is maintainedbetween the shaft 46 and the bevel gear 44 at any position of theupright 22 along its supporting surface 26 on the bed.'

The splined shaft 46 projects forward through the face of the bed 2i andis provided near its forward end with an actuating worm wheel 41 Ithatis housed within a bracket 46 fixed on the front vof the bed. as shownin Fig. 1-. 'I'he worm wheel 41 is engaged by a vertically disposed driving worm 6I` which is rotatably mounted in the bracket and is connectedat its lower end to the shaft of a vertically positioned electric motor52 that is flanged to and depends from the bracket 46. At its upperiend,the worm 6| is connected to a short shaft 63 projecting upwardthroughthe top of the bracket `43 and carrying at its uppe: end an exposed handwheel 64, the arrangemeni being such that the spindle head 26 may bemoved by power by means of the motor 62 approximate- Vly to apredetermined position and then adjusted precisely to the desiredposition by manually actuating the hand wheel 64.

For indicating the position of the'head 26 apasoman act position of .thehead, a sensitive dial indicator 88, shown in Fig. l., is carried by thehead and connected with linkage disposed to cooperate with the upper endof avertically disposed measuring rod 51 of predetermined length, thelower end of which engages an abutment or anvil 5I on a hori- 'rocaviste the possibmty or the head 2s being moved under power-beyond safelimits, the up-4 right 22 is provided with an upper limit switch el anda lower limit switch 62, arranged to be actuated, upon 'engagement bytrip dogs on the head at lthe respective ends of its course of verticaltravel and operatively connected to ie-energize the motor 52. To insureagainst accidentally bringing the ram 21 d'own upon the work surface doof the bed, the head 26 is provided on its lower surface with anextending trip element or dog di! that is arranged to contact andactuate the lower limit switch 62 before the ram' reaches the tablesurface, the dog 83 being removable to permit further lowering of thehead under control of a iixed limit dog when the ram is being operatedin retracted position. Operation of the motor 52 in the one or the otherdirection to cause raising or lowering of the head 25, is effected bymeans of controlling push buttons 64 and $5 mounted on a control panel66 projecting upward from the right iront corner of the bed 2l.

Horizontal adjustment of the upright 22 along the supporting surface 25is eiected by means ci a horiozntally disposed screw 1|, best shown inFig. d, whichcooperates. with a nut 'l2 depending fromvand fixed to thelower surface of the upright. The screw 1l extends through the iront othe bed 2l into the bracket 48 and is p'rovided on its extendingend'with an actuating worm wheel 'i3 similar to the worm wheel 41 foreecting vertical movement of the head. As appears in Fig. l, the wormwheel 13 is housed within the bracket 4i) adjacent to the worm wheel 41and is similarly engaged for operation by a ver' tically disposed wormi4 the lower end of which l is connected to a vertical positioned`.traversing motor lo and the upper end provided with an external handwheell for manual actuation.` To

indicate approximately the extent of movement p measuring rods 82interposed end to end between the indicator and the base of the upright.As shown in Figs. .4 and 5, the measuring rods 82 al're supportedin aV-shaped groove or trough formed in a 'guide member 83 ilxed in thesupporting surface 25 of the bedl 2|. The rods 82 are engaged at theinner end by an abutment element 84 fixed on the lower forward surfaceof the upright 22, and, they engage at the outerend a sliding plunger88-and 88-may be actuated simultaneously, each- 88 on the control panel86.

8l. The plunger I8 is arranged to engage at its other end the operatingstem of the dial indicator which resillently'urges it in directiontoward the i upright. The plunger is slidably. mounted for free movementin a sleeve '88 that is in turn slidably mounted ina bore in the bracket4i. 'By this arrangement, the upright 22l may be moved a predetermineddistance by iirst setting the dial` indicator 8i to a known position incooperation with a measuring rod combination of known length and thensubstituting for the known measuring rod 82 another measuring rodcombination differing in length by the amount of movement required.after which the upright 22 is moved until the indicator 8| is returnedto the known position by action of the new measuringrod.

To avoid injury to the mechanism in the event that the upright 22 ismoved by power into eni gagement with the measuring rod 82, there isprovided in the bracket 48 a forward limit switch 81 that is arranged tobe actuated by a cam 88 on the sleeve 86 `when it is moved forward bythe i measuring'rod, and that functions to de.energ ize the motor 15which drives .the screw 1I. As shown, the sleeve 86 is provided with a.slot 88 that affords a lost 'motion connection with a. cooperating pininthe plunger 85. A coil spring 98 associated with the sleeve 88 servesto urge itthe hand wheel 18 to move it to the position indicated bymovement of the dial indicator .pointer to its original known position.-In the event jthat there is no measuring rod in the guide member 88,the upright 22 will be stopped at the forward end of its course oftravel by the engagement of a trip dog 8i that projects forward from theupright 22 with the spring urged sleeve 8l carrying thecam 88A whichcontrols thehimit switch `81. As shown in Fig. 5, the trip dog 8i is oirectangular br square shape in section and is arranged to operate in acomplementary groove formed in the guide member 88 at the bottom y oi'the rod receiving V-groove.

To prevent movement of the upright 22 too -far in the other direction,there is providedv a second or rear limit switchi82, shown in Fig. 5,

mounted in the base 2i beneath 'the upright in position to be engaged byan actuating cam S8 depending from the bottom of the upright.

Energlzation of the motor-,15 to causegmovement of the upright 22 in theone or the other direc tion. is effected by means of push buttons 911and As best shown in Fis. 5, the upright is fitted in ways 8i formedon-the supporting surface 2 8 and adjusted thereto by means of a gib 81.After the upright 22 has been moved to the predetermined position ofadjustment, it may be clamped to the supporting surface 2i by means oftwo spaced clamping T-bolts v88 and 88 that are carried by the uprightand that operate along a cooperating T-slot |84 in. thelbed 2i. Inorderthat the bolts bolt is provided with a cooperating nut 482 having aradially extending arm, the ends of the Control of the power operationof the entireY machine is eifected by master push buttons |05 and |08mounted at the top of the control panel 68. Another set of controlbuttons, |01 and |08 serve to control the motor of a coolant pump unit I03 that functions to provide coolant liquid to the cutter 32 driven bythe spindle 28.

Power for rotating the cutter driving spindle' 28 and for effectingfeeding movement of theram 21 is derived from a spindle driving motor I0that is mounted on the spindle head 26 for bodily movement with it. Asappears in Fig. 1, themotlr ||0 is connected to drivea speed changingmechanism housed within the spindle head 26. thatI is arranged toprovide a predetermined driving ratio upon being adjusted by means of anadjusting crank 4and cooperating speed indicating dial mechanism mountedon the forward side'of the head. Power at the selected speed ratio isl.transmitted by means of a. splined shaft ||2 to -4 an upwardlyextending housing l I3 carried on the rearward end of the horizontallysliding ram 21, the arrangement being such that driving connection ismaintained regardless of the position of the ram in itsslidingmovement., As shown in Fig. 6, power from the shaft ||2 vis transmittedto the spindle 28 by means of a range changing gear couplet ||3 withinthe housing I i3 that may be shifted to either a high speed range or alow speed range position by means of a range changl slot |32 inAifhebrackei: |35.' may be tightened f4) ing lever 5 mounted on thefront of the housing,

the arrangement being such that the spindle 28 may be driven at anyspeed within the combined ranges of the speed changer and the rangechange couplet ||4. i

Power for effecting axial feeding movement of the ram 21 is derived fromthe spindle 28, the

arrangement being such that the ram may be moved in synchronism withrotation of the spindle to provide for effecting. thread 'cuttingoperations. As shown in Fig. 6, the spindle 2B is provided for thispurpose with a spur gear 8 that meshes with a spur pinion IIS rotatablymounted in the housing ||3 on an axis parallel with the spindle. Thepinion I8 is connected with a bevel pinion |20, as best shown in Fig.'1, that meshes with a complementary bevel pinion |2| on the inner endof a shaft |22 that projects transversely into a gear chamber |23 at thefront of the housing ||3. The shaft |22 is provided within the chamber|23 with a gear |24 -and a pinion |25. 'I'he pinion |25 provides for alow range of feeding movement and has meshing engagement with arelatively large gear |26 that is connected with another pinion |21. Thegear |24 lprovides for a high range of feeding movement and is disposedto mesh with a gear |28 of substantially equal diameter. A shiftablerange changing couplet |3| is slidably splined on a shaft |32 in mannerto be movable into meshing engagement with either the high speed rangegear |28 or the low'speed range gear |21. Shifting movement of the rangechanging couplet |3| is accomplished by means of a range changingv shiftlever |33,

. shown in Figs.V 1 and '1, 4at the end of the gear chamber |23. Thelever '|33 may be turned to actuate` a shifting fork |34 which engagesthe couplet |3| in manner to slide it along the splined lshaft |32 andit has a neutral position in which the couplet is disengaged from boththe low speed pinion |21 and the high speed gear |23.

The splined shaft |32 projects outward from the chamber |23 into a leadchanging pick-oi! gear chamber |35 at the side of the housing 3, towhich access may be had by opening a hinged cover-|31. The end 0f theshaft |32 -within the chamber |35 is adapted to receive a removablepick-off gear |4| that meshes with a complementary pick-ofi' gear |42Journalled on a spindle |43 that is slidably iitted in a slot |44 of a.change gear bracket, as best shown in Fig. 8. The gear |42 is connectedwith a smaller gear |43 in manner to constitute a couplet, and the gear|45 in turn meshes with another pick-off gear |41 that it removablyfitted on the end of a driven splined shaft |48. The pick-olf gearsbetween he shafts |32 and |48 constitute a rate `or lead changingmechanism that functions in cooperation with the range changing couplet|3| to drive the ram in axial feeding movement at any one of a multi---plicity of rates.

'As best shown in Fig. 8, the change Bear bracket |45 is pivotallymounted concentric with the shaft |48, the arrangement being such thatthe spindle |43 may be moved along the slot |44 to mesh the gear |48with the gear |41, and the bracket |45 may then be pivoted about theshaft |48 to mesh the gear |42 with the driving pick-oil! gear |4|.After the gears have been meshed, a nut |50 on the spindle |43 may betightened to clamp the spindle in adjusted position in the slot |44 ofthe bracket |45, and a clamping bolt |5| which operates in an arcuate|53 into driving engagement with either bevel gear. As indicated inPigs. 6 and 1, the shiftmg fork m is arranged to be actuated by sreversing lever |30, mounted ,on the end of the gear chamber |23, thelever being movable to two positions for forward and reverse operation,

respectively, in controlling the direction oi' feeding movement of thespindle 28. The lever |55 is secured to the end of a control shaft I 5|rotatably mounted in the upper part of the chamber |23, the other end ofthe shaft being provided with a cam element that engages the shiftingfork |58 in well known manner to eifect sliding move-` ment thereof.

As appears in Figs. 'I and 9. the reversing bevel gears |55 and |51 bothhave meshing engagement with a complementary bevel gear |33. thearrangement being such that the gear |33 may be driven in the one or theother direction depending upon which of the meshing gears|53 and |51 isengaged by the clutch collar |35. The bevel gear |53 is fixed on the emiof l. splined shaft I 54 which is disposed parallel with the spindle 28and is rotatably supported by bearings |35 in the wall of the gearchamber |23. As appears in Figs. 1 and 9, the shaft |53 extends forwardfrom the gear chamber |23 into a hollow shaft or sleeve |53 that isrotatably mounted on 2,ss7,eco

me covered by Patent No. 1,968,276 to'Jsepnarranged to telescope toaccommodate movement of the ram 21 and its associated gearing relativeto the spindle head proper.

A selectively engageable driving connection is effected between 'thesplined shaft |68 and the hollow sleeve shaft |89 by means of an axiallyworm element |18 that is disposed to mesh with and drive ka worm wheel|18 on a transverse shaft |11. As best shown in Fig. 10, the shaft |11is provided at its inner end with a pinion |16 that meshes with` a rackelement |19 ilxed on the ram 21, the arrangement being such thatrotation of the hollow shaft |60 in the one or the other directioncauses advancing or retracting movement of the ram. As shown in Figs. l

and 9, the shaft |11 is provided at its -forward end with a. large starwheel or pilot wheel I 9| I. by means of which the shaft may be-turnedman- B. Armitage. As best shown in Figs. l andJ 9, the turret stopmechanism |89 is mounted on the front of the ram gear chamber H3 andcarries a plurality of adjustable stop rods or measuring rods |90arranged to be moved selectively into f operating position. Themeasuring rod |90 that ually to move the ram 21 at rapid rate, a clutchbeing arranged between the shaft |11 and the worm wheel |16 forreleasing the shaft for manual rotation, as more fully explained in thepreviously mentioned Patent No. 2,263,404. To prevent unintentionaldisengagement of the star l couplet i3! in combination with the ratioestab-4 lished by ther pick-oir gears in the chamber |39, and in thedirection established by the position of the reversing clutch spool |58.Since the ram feeding mechanism is driven directly from the spindle 20,the advancing movement of the ram is definitely correlated with rotationof the Spinsleeve |81 and the star dle for effecting screw threadcutting or similar spiral operations, the pitch or lead of the spiralbeing determined by the driving ratio of the ram feeding train. Afterthe desired driving ratio has been established, the actual speed of thecutting operation may be regulated by adiusting the 'spindle drivingspeed changing mechanism in the spindle head 26. To provide for closemanual adjustment of the` position of the ram.

21, the sleeve shaft |66 is fitted at its forward end with a handwheel|94 that carries a micrometer dial |85 for indicating the extent ofmovement effected.

When the machine is being utilized to effect a boring opera-tion, it isdesirabe to feed thel cutter spindle forward under power until thecutter approaches the predetermined position at which the cuttingoperation is to cease. The power drive is then automaticaliy disengagedand the feeding movement continued i :mualiy by actuation of the handwheel SM. explained in the previously' mentioned Patent No. 2,263,404.,power advance of the nur maybe automatically tripped out at any one ci'preeeiected positions by operation of e turret stop mechanism ld of theis inthe active position is ldisposed to abut the end oi' anactuatingplunger |9| when the ram advances to the position for which the rod isadjusted. As shown, the plunger |9I is slidably mounted in the head 28and is provided with a slotted sleeve |99 which engages the lower end ofa pivoted lever |96. The upper end of 'the lever |94 engages -the groove|13 -of the shiftable clutch sleeve |61, thearrangement being such thatwhen the plunger is moved to theleft by the advancing ram, the lever |94will pivot to move the teeth |66 of the clutch sleeve |61 out ofengagement with the clutch teeth |69 on th'e shaft |66, therebyinterrupting the power driv- Y ing train for the rain feeding movement.

After advancing movement of the ram by power has been stopped by thetrip mechanism, further movement to4 a precisely predetermined positionmay be effected manually by turning the hand wheel |95. For determiningthe position of the 'ram precisely in order to terminate the boring'operation at a predetermined point, there is provided a sensitive dialindicator mechanism |95 mounted on the head 28 above the indicator 86.As shown in Fig. 9, .the plunger 19| which is engaged by the turretstop. rod |90 at its protruding end is arranged to engage at its otherend with the stem ofthe dial indicator I 96. As

the ram is yadvanced by turning the hand wheel i90, the dial indicatoris actuated by the plunger |9| to show Vwith a high degree of accuracythe arrival of the ram at the predetermined position,v the cutterspindle 29 meanwhile continuing to operate to complete lthe cut. If itis desired to retain the ram in the position to which it is adjusted, itmaybe clamped rigidly to the head 26 by actuating a clamping lever.|96in the manner more fully explained in previously mentioned Patent No.2,263,404. l

Y In performing a threading operation suchas that illustrated in Fig. 1,it isdesirable to ar,- range for retracting the. cutting tool 32 yafterit has arrived ata predetermined inner limit, by turning -it backwardalong the threads already cut. operation is discontinued withoutdisengaging the feed driving train and the cutter then retracted byoperating the spindle driving mecha- 'nisne in the reverse direction. Tothis end, a

limit switch iti is arranged to de-energlze the 'spizidie driving motoril and engage an electrihv erzergcingthe motor llt for operation 'in thecally operated brake 202 for stopping the forward movement of the cutter92 promptly at the end oi a threading operation. As shown in Fig. 9, thelimit switch 29| is arranged to be actuated by a spring urged plunger204 that cooperates with. a' carn'surface 209 on the indicator actuatingplunger |9| the arrangement being such that when a step rod engages theplunger |9| at the end ci' an "out movement of the ram, the' limitswitch 29| will be actuated to stop thev drivier-.g motor Mii before theclutch sleeve |61 can be moved to disengaged position. Retractingmovement ci the threading cutter 32 along the dreads out in the workpie-ce 33 is then effected reverse direction. Since the ram drivingmech# anti-un remains engaged. a second cut vzrnaythen 'To accomplishthis, the forward feeding l work supporting surface 23.

6 aaasao ram. Control oi' the motor ||5 is effected by means of ramadvancing and ram retracting push buttons 258 and 259, respectively,mounted in a pendant station 2|0 that is suspended above the workreceiving surface 25 from the .end of Va radiusl arm 2|| pivotallymounted on the top of the upright 22.

To prevent the ram -21 from being retracted by power beyond apredetermined limiting position, a second or inf limit switch 2|5 isprovided for stopping the motor H5 and applying the brake 2|l2.y Asshown in Fig. 10, the retacting limit switch 2|5 is arranged to beactuated by means of a cam 2|! nxed on the surface of the ram 21 inposition to .engage a spring pressed radially disposed plunger 2|5 whenthe ram arrives at its retracted position. 'I'he plunger 2|5 engages aball 2|t which acts. upon a second plunger 2|1 disposed in horizontalposition, at an angle to the plunger 2|5, and operatively conlzi'egtedthrough linkage 2|5 to actuate the switch The outboard supportingstructure 29 which "carries the outer end of the arbor 5| supporting thecutter 32 as indicated in Fig. 1, is shown more in detail in Fig. l1. Asappears in the drawings, the end o f the arbor 3| is rotatably andslidably received in a journal bearingv 22| formed in a bearing block222 that i2; slidably mounted for vertical adjustment between ,sidemembers 223 and 224 constituting an upright guiding element. The bearingblock 222 may be adjusted vertically along the upright to bring thejournal bearing into alignment with the spindle 25, by means of athreaded shaft 225 that is disposed in vertical position and journalledat and thathas threaded engagement with anuty 235 formed in the lowerend of the side member 225. The screw shaft 231 projects at the rear ofthe machine. as shown in Fig. 2, and is pro' vided with a squared end255 for receiving a crank or the like to effect the lateral adjustment.A micrometer dial 25| is associated with the shaft 231 for indicatingthe extent of the movement effected. For performing milling operationsin restricted spaces, the machine may be fitted with an attachment ofthe type shown in Pigs. l2 and 13 'I'his attachment is arranged to bemounted on the forward end of the ram 21 and functions to effect aslotting operation, for example, such as may be required in cutting akeyway 255 within a cylindrical opening 255 formed by a previous boringoperation in a work piece 251. As shown, the attachment is constitutedby a base or body portion 255 provided .with upper and lower lugs 25|which are secured to the upper and lower slide elements of the ram 21 bymea-ns of bolts or cap screws 252. A third. intermediate lug 253projects from the body 255 toward the front of the machine and carries ahook bolt 255 that engages a-slot 255 cut in the forward side of the ramas shown in Fig. 1.

The base orhousing 255 has rotatably mounted thereon a cutter head 251presenting a narrow cutter carrying projecting arm 255 disposedcoaxially o f the spindle 25, from which a slottins cutter 255 projectslaterally. the arm being arits ends in the top and bottom of the uprightin manner to have threaded engagement with a nut 225 formed in the block222. The shaft 225 may be turned by means of a bevel gear 221 fixed onits lower end and meshing with a similar bevel gear 225 fixed on theinner end of a horizontal shaft 225 that is journalled in the lower partof the side member .223. As shown. the shaft 229 projects toward thefront of the machine and is provided at its outer end with a squaredportion 250 for receiving a crank or the like by means of which thevertical adjustment may be effected. Associated with the outer end ofthe shaft 229. is a micrometer` dial 23| for indicating the extent ofvertical movement ofthe bearing block 222. After the bearing block hasbeen moved to adjusted position, it may be clamped in place bytightening a clampingbolt 232 which extends through the block andoperates to draw the side members 223 and 225 toward each other intoclamping engagement with the sides of the bloclr.v A hand lever 233 isprovided on the forward end of the rod 232 for turning it to eHect theclamping action.

To provide for'adjusting the position of the supporting journal22|'laterally into alignment with the spindle 25, the -upright guidingelement -of the outboard support,.constituted by the side members 223and 225, is slidably fitted in a base 235 which is secured by theT-bolts 35 to the in a lug 255 projecting upward from the has@ Asappears in Ilig.

` ranged to carry the cutter into a restricted opening such as the bore255.

For adjusting the angular position of the projecting eutter 255, the

head 251 may be turned angularly relative to the base 250. To effect theangular adjustment,

the head 251 is provided with an emular worm wheel 25| extending withinthe housing 255 in position to have meshing engagement with a worm 262journalled transversely of the housing. The worm 282 is formed on ashaft 253 provided with a' squared projecting end for receiving a crankor the like to turn the worm in effectingt 'the angular adjustment. Ascale 264 is provided on the periphery of the rotatable head 251 forindicating its angular position. After the cutter has been adjusted tothe desired angular position, the head 251 may be clamped to the housing250 by tightening T--beits 251 which project forward through thl; headand operate in an annular T-slotl 268 formed in the forward face of thehousing 25u.

Power for driving the cutter 259` is derived from the main spindle 25.the end of which is engaged by a driving collar 21|. VThe collar 21| isfixed on a shaft 212 that is'journailed in the head-251 concentric withits axis of rotation. The shaft 212 is provided at its forward end witha bevel gear 215 which has meshing engagement with a smallercomplementary bevel gear 215 fixed on a transverse shaft 215 supportedat itsl ends in bearings in the head-2n. The shaft m is provided at itsmid-portion with a spur gear' 211 which in turn meshes with .the firstof a train of `spur gears 215, 215 and 255 rotatably mounted within theprojecting arm 255 in position to transmit power along the axis of thehead 251. The last gear 255 of the train meshes with a similar spur gear25| mounted on a hollow spindle 252 into which the slotting cutter 255is fitted.

In operating the machine with the slotting attachment in place'on theend of the ram 21, the

head 251 is ilrst adjusted angularly to bring the cutter 253 intoposition to form a slot at the desired angular'relationship to the bore,and the -head clamped to.the body 250. The speed changing gearing andthe feed changing gearing ot the spindle head 26 are then adjusted andthe main motor H started in direction to effect forward feeding movementor advance of the`ram.

With the gearing properly adjusted, the cutter and L3. As previouslymentioned, the operation of the entire machine is under the control ofthe master push button switches and |03 thatfunction to energize or,de-energize 'the control circuit for actuating the relays and switchesassociated with the several motors. vWhen the master starting pushybutton switch |05 is depressed, it closes an energizing circuit leadingfrom the line conductor L2 through a conductor the previously mentionednormally closed,

master stop pushbutton |05, a conductor 302, the closed push buttonswitch |05 and a conductor 303 leading to an actuating coil 304 of amaster relay 305, a return conductor 303 'then completing the circuitfrom` the coil to the line conductor L|. y l

With the actuating coil 304 thus energized, the relay closes andenergizes a control supply circuit which extends from'the line conductor'LI through the conductor 305, a branch conductor 301, and closedcontacts 303 of the relay305 4toV a control source conductor 303. Areturn control source conductor 3|0` is y-simultaneously con` nec'ted byclosed contacts 3|| of the relay 305, to a conductor v3|2 which connectswith the conductor 302 leading tothe push button |00 from which theconductor 30| returns to the line conductor L2. Simultaneously,` anotherclosed contact 3|3 of the relay 305 establishes a holding circuit lnshunt relationship with the normally open master starting, push'buttonswitch |05.

^ The holding circuit thus established extends from the line conductorL| through the conductor 303,

'dle head 23its actuating motor 52 may be energized to turnvin therequired direction by depressing the ".up" pus-'h button 34, aspreviously mentioned. This results in completing acontrol circuit.extending from the control source conductor 303,-fthrough a branchconductor l,3|3 and.

the closed push button switch `|54, to an actuating coil 3|3 of a motorcontrolling switch 320. From the coil 3|3, the circuit returns throughafcon-" ductor 324 returns to the other control sourcesconductor 3|0.With'the actuating coil 3|3 thus energized, the motor switch 320 isclosed to. effect a connection from lin conductors Ll, L2 and L3 to themotor 52 to cause it to operate in a direction resulting in upwardmovement of the spindle head. With the motor 52 thus energized, the headwillcontinue to move upward until the push button 54' is released oruntil the upper limit switch 3| is engaged to hpen the control circuit.y

For eiecting downward movement or theA spindle head 23, the previouslymentioned down push button 65 is depressed to close a. control eircuitleading from 'the control source conductor 303, through lthe conductor3| 8 and the closed push button 55, to an actuating coil 321 of a motorswitch 328. From the coil 321, vthe circuit re- 'turns through alconductor 323, the-lower limit` switch 32 and the conductor 322 thatleads yto the-i overload relay 323 from which the conductor 32,4Vreturns to the control source conductor 3 0. .f With `the coil 321energized, the switch 323 closes and eiects a reversed connection fromthe linefcol ductors Ll, L2 and L3. to the motor 52, causing it y tooperate in direction for moving the head-down.-

ward. With the motor 52 thus energized for rei versed operation,downward movement of the head will .continue until the push button 55 isreleased or the lower limit switch32 is opened.

Movement of the upright along the base is controlled in similar manner,1the forward push button 3 4 beingfdepressed tocausethe' motor 15 to turnin direction to move'the upright toward the front of the machine. Asshown in the wiring di agram, this completes a control circuit from thecontrol source conductor 303, through a branch v conductor 33|, theclosed push button switch 34, an'actuating coil 332 of@l motor switch333 and thence through a conductor'334, the closed forward limit 1switch31 and a conductor 335 4leading to an overload relay 335 associated withthe motor 15, from which' a conductor 331 leads to the control sourceconductor- 3|0. Upon closing the motor switch 333 by energizing the coil332. in this manner, the motor 'I5 is energized from the line conductorsLI, L2 and L3 in manner to effect forward movement of the upright, thevmovement continuing until the push button 34 is released or the forwardlimit switch 31 is opened.

For moving the `upright toward the rearofthe machine,` the previouslymentioned push b'utton 3,5 is depressed to complete a circuit from thecontrol conductor 303 through the branch conductor 33|, the closed pushbutton switch 35, an energizing coil 340 of a motor switch 34|, aconductor 342, the closedrear limit switch 32 and thence through theconductor 335, the overload4 relay 335 and conductor 331 to the returncontrol conductor 3|0. Energization 4oi the actuating-col1340 results inclosing the switch 34| to eiect a reversed connection from the lineconductors L|, L2 and L3 to the motor 15 to cause it to turn indirection to effect rearward -movement of the upright, the movementcontinuing until the button.

35 is released or the limit switch 32 is openedat the end of the courseof travel. The motor `for actuating the coolant pump unit |03 islikewise arranged to be energized from the line conductors Li, L2 and L3under thecontrol of the previously mentioned push buttonsl |01 and |03,but since the control circuit for this motor is of standard, well knowntype it has not been-illustrated in the wiring diagram. i n

The spindle driving motor ||0 is provided .with power line conductors345, 345 and 341 that are movement of the ram until the outer arrangedto be connected to the line conductors Li, L2 and L3, either directly orin reverse order, by one or the other of two motor energizing switches300 and 343. lIfhese switches are arranged to be controlled by thepreviously mention'ed ram and spindle controlling push buttons 203 and209 carried by the pendant station 2|0. Upon depressing lthe ramadvancing push button 200, a control circuit is established which leadsfrom the line conductor Ll through conductor 300,

2,sa7,sao

ner 11minswitch zu, the conductor m, and a conductor 310, to the otherpole of the closed branch conductor 301, closed contact 300 oi' the'lenergized master relay 300, the control source conductor 300, the closedouter limit switch 20|,

a conductor 3 52, the closed push button switch 203, a conductor 353,closed contacts 300 of a dln rection selecting or conditioning relay 355and thence by a conductor 356 to an actuating coil 351 of the motorswitch 300. From the coil 351, the circuit returns through a conductor`350 to an overload relay 353 in the power lines to the motor I| 0, fromwhich a'conductor 360 leads to a normally closed emergency stop switch30| mounted on the lower end of the pendant station 2 I 0. From thependant stop switch 30| thecircuit continues through the conductor 3|2,conductor 302, stop push button |08 and conductor 30|, to the lineconductor L2.

Energization of the coil 351 closes the switch 349 to cause the motorIII to operate in a predetermined direction, and simultaneouslyestablishes a holding circuit in shunt relationship with the push buttonswitch 200. The holding circuit leads from the control source .condutor'300 through the outer limit switch 20| and a conductor 363 to one poleof a double pole inching selector or conditioning switch 30|. With theinching switch 364 closed, the circuit continues through a conductor360, closed contacts 306 of the direction selecting relay 355, andthence through a conductor 301 to closed interlocking contacts 368 oi'theenergized motor switch 309 from which a conductor 300 leads to theswitch actuating coil 351. The holding circuit thus established retainsthe switch 300 in closed position even though the push button 208 may bereleased, and causes the motor tol eiect advancing limit switch isengaged and opened.

In similar manner, when the ram retracting push button 209 is depressed,a control circuit is established from the line conductor Li through theCIOSed master relay 300 and the control source conductor 309 to theclosed inner limit switch 2|3 from which a conductor 312 leads to theclosed push button switch 200. From the switch 200 a conductor 313 leadsto closed contacts 310 of the direction selecting relay 300 and thencethrough a conductor 310 'to an actuating coil 31.0 of the 'other spindlemotor switch 340. From` the coil 310, the return circuit leads throughthe conductor 350, overload relay 359, conductor 300, peninchingselector switch 380 from which a conductor 310 leads to closed contacts300 of the direction selecting relay 300 and thence through a conductor33| to interlocking contacts 302 on the switch 300 from which aconductor 303 leads to the switch actuating coil 310. This holdingcircuit functions likewise to retain the switch 300 in closed positionafter the push button 203 has been released, the motor ||0 continuing toop-l crate to efi'ect retracting movement of the ram until the innerlimit switch 2|3 is engaged and opened.

As previously mentioned, the brake 202 associated with the' motor ||0 isarranged to be engaged automatically upon stopping themotor at the endofthe course of vtravel of the ram. For automatically releasing thebrake when the motor I|0 is energized by closing either the motor switch348 or the motor switch 300, a brake'releasing circuit is establishedwhich extends from the motor conductor 341 through a conductor 385,closed contacts 380 of a brake controlling relay 301 and thence througha conductor 300 to the brake 202. The return circuit extends from theVbrake 202 through a conductor 300.

'closed contacts 30| of the brake relay 331 and a conductor 302 to themotor supply conductor 306. With the brake controlling relay 331 in thef position shown in Fig. 14. energy is provided to release the brakewhenever the spindle motor I |0 is energized. In the eventthat itis-desired to operate the spindle motor according to a mode oi'operation in which the brake is not engaged when the motor is stopped,energy for retaining the brake in released position continuously may beobtained dant stopswitch 36|, conductor 3|2 and conduc- Y tor 302 to themaster stop push button switch |00 from which the conductor 30|- returnsto line conductor L2.

With the coil 310 energized, the motor switch 330 closes to eii'ect areversed connection between the line conductors LI, L2 and L3 and themotor power conductors 34|, 303 and 301 thereby ef. fecting operation ofthe motor lil in direction opposite to that eiiected by closing theswitch 340. Likewise, the closed switch 300 Aestablishes a holdingcircuit in shunt relationship with the push button 203. This holdingcircuit leads from the control source circuit, whenever the conductor33| through the in- 75 desirable that the directly from the lineconductors by energizing' and thereby repositioning the brakecontrolling relay 381. Energization of the brake relay 301 is effectedby closing a brake controlling switch 390, mounted on the pendantstation 2|0, which results in completing a circuit from the controlsource conductor 3| 0 through the-closed switch 304 and a conductor 395to an actuating coil 330 of the brake relay 381 from which the circuitreturns through a conductor301 and the inner ram limit switch 2| 3 tothe other control source conductor 303. Energization of the coil 390moves the relay 381. upward from the position shown in the drawings, toopen the contacts 300 and 33| and close contacts 300 and 300. Thisresults in establishing a direct connection from the line motor |I0 isenergized. ,Howeven since the inner limit switch 2|3 is in the brakerelay controlling ram in retracted to the position at which the innerlimit switch is opened, the brake relay coil 303 will be de-energizedand the relay 331. will move to the position in which the brake isdisconnected from the line conductors, whereupon the motor will bede-ene'rgized and the brake will be engaged at the same time to stop themotor quickly and prevent excessive inward movement oi' the ram.' o Whenthe machine is being utilized to etl'ect a boring operation to apredetermined depth,'it is final feeding movement be effected manually,as previously explained, by

actuating the hand wheel |84 in order to move the`cutter toa positionprecisely indicated by the.

- trol rod l 9| which also serves to actuate the out" limit switch 209.Since the limit switch is arranged to function before sufficientmovement of the rod |9i has occurred to disengage the clutch,

it is necessary that'the limit switch be rendered f 'inactive wheneverit is desired to enect a boring operation in this manner. For thispurpose, the brake selecting relay 381 is provided with an auxiliarycontact 408 that is arranged to be closed when the brake selectingswitch 39d on Ithe pendant station is closed. This establishes a circuitin shunt relationship to the out limit switch 20| extending from thecontrol source 309 through a conductor 509, the closed contacts 408 anda conductor 4|0 which leads to the conductor 352 at the other side ofthe. limit switch 20|. With the limit switch 20| thus shunted out of thecircuit, the ram 21 may be advanced in a boring operation until theturret stop |89 effects disengagement of the clutch sleeve 861. Feedingmovement of the ram will then cease while rotation of the cutter spindle26will continue. The ram may then be .advancedmanually by means of thehand wheel |84 until the indicator .|88 shows that the boring operationhas proceeded precisely to the predetermined position.

, For effecting intermittent operation of the spindle motor under thedirectional control of the push buttons 208 and209, as may be desirablewhen setting up the machine prior to operating upon a work piece or whenshifting thespeed changing gearing, the circuit maybe adapted to thismode of operation by opening the inching selector switch 364. Thisinterrupts the holding circuits for the motor switches 348 and 349thereby permitting the switches to open upon release of the respectivepush buttons, making themotor Ity directly responsive to closing oropening of the push button switches 208 and 209.

As previously mentioned, the spindle motor controlling push buttons 208and 209 are designated to effect spindle advancing and spindleretracting movements respectively, this being ef ected by' operating thespindle motor H0 in the one or the other direction. For boringoperations, the cutting tool ordinarily can be arranged for operation inthe direction corresponding to the desired feeding response obtainedfrom operation of the directional push buttons. However,

lfor some operations, such as thread cutng, it is necessary that thespindle turn in one or the other direction relative to advancingmovement ofthe ram, as may be required for cutting righthand orleft-hand threads or similar operations. This desired relationship ofmovements is established by properly positioning the ram feed re-Vversing spool |58 through actuating'the reversing lever |60. In order tomaintain the directional.

As previously explained, the ram advancing push button 208 is connected,when the direction selecting relay 955 is in the position shown in thedrawings, to effect control of the motor switch 349, while'the ramretracting button 209 effects control of the switch 348. If now it isdesired t0 change the relationship of spindle rotation to ram movement,the ram reversing lever |60 is moved to its other position and thedirection selecting relay 355 is likewise shifted to its other.

position to reverse the controls.

As shown in the wiring diagram, the direction relay 355 is controlled bymeans of a direction selecting switch 4 l2 that is mounted on the pendant station 2|0. When closed, this switch estabswitch 348. Likewise, theconnection through` the holding circuit leading from the fout limitswitch 20|, through contacts 366 of the direction,

selecting relay, to the holding contacts 368 of motor switch 349, isopened and a new holding circuit established by` closing a contact 4 I8of the relay which eiects a connection through the conductor 38| to theholding contacts 382 of the switch 348. y

In like manner, ram retracting control button 209 isdisconnected frommotor switch 348`-by opening contacts 314 of the directional relay andanew circuit established through contacts 4|9 which connect to theconductor 356 leading to the actuating coil 351 of motor switch 349. Theconnection through the holding circuit leading from the in limit switch`2|3 to motor switch 348 is also broken by opening contacts 380 of therelay 355 and a new holding circuit connection established throughcontacts 420 which connect with conductor 361 leading to the holdingcircuit contacts 368 of motor switch 349. With the control circuits thusrearranged by shifting the direction selecting relay 855, the ram 21will respond to the advancing and retracting push buttons 208 and 209'in the same manner asbefore reversal of the ram feeding train by thereversing lever |60 but with the spindle operating in the otherdirection to cut the required helix.

The pendant stopswitch 36|, being in the return circuit from the spindlemotor control to the line conductor L2, is not eiected by operation ofeither the brake selecting relay 381 or the direction selecting relay355 and continues to be operative to de-energize and stop the spindlemotor I0 whenever it is moved to open position,

ergency.

From the foregoing explanation of the boring and threading machineherein set forth to exemplify the present invention, it will be apparentthat there has been provided an improved machine tool especially adaptedto perform boring and threading operations and-the like with a highdegree of einciency and accuracy.

Although the mustrative embodiment of the invention has been describedin detail for vthe purpose of setting forth a practical exemplifylngstructure, it isto be understood that' the particular apparatus hereindescribed is intended to be illustrative only and that variouscharacteristics of the invention may be incorporated in other structuralforms without departing from the spirit and scope. of the invention asdeiined "5 inthe subjoined claims. 'Ihe principles of thexinventionhaving now been fully explained in connection with the iore- 'goingdescription of an illustrative preferred embodying structure, we herebyclaim as our invention ordiscovery:

1. In a threading machine, a ram arranged for axial feeding movement, acutter carrying spindle rotatably mounted in said ram. an electric motoroperatively connected to drive said spindle', feeding mechanismoperative to eect feeding movement of said ram and arranged to be drivenby said spindle, said Yfeeding mechanism includgear and operative tocondition said directional' switches to effect the desired movements ofsaid ram without regard to the direction of rotation of said electricmotor and ,said spindle, whereby either right hand or left hand threadsmay be cut under similar` conditions of control as to direction offeeding movement.

2. In a boring and threading machine, a spindle carrying ram arrangedfor axial feeding movement, a cutter carrying spindle rotatably mountedin said ram, an electric motor operatively connected to rotatesaidspindle, a transmission train including reversing and rate changingmechanism connected to be driven by (said spindle and operative to eectfeeding movement of said ram, control mechanism for said motor includingforward and reverse ram operating switches, and a control switchassociated with said mechanism and` operative to condition said controlmechanism to provide for maintaining the directional effect of said ramoperating switches regardless of the direction of rotation of saidspindle, whereby threading operations to form either right hand or leftthreads may be controlled by said ram operating switches withoutconfusion regarding the direction or rain feeding movement. 3. In aboring and threading machine, the combination with an axially movablespindle carrying ram, a cutter supporting spindle rotatably mounted insaid ram, power driven' means operatively connected to rotate saidspindle in either direction selectively, and means driven 'by saidspindle and operatively connected to eiect axial feeding movement ofsaidram and spindle in either direction selectively for performing aboring operation, of control apparatus selectively,

operable to condition said machine for thread spindle may be advanced ina threa ;ilng cutvto v and stopped precisely at a predeterminedposition.

cutting, comprising a selectively engageable brake operative to stopsaid spindle rotating means quickly, trip mechanism operative todiscontinue driving said spindle and to apply said brake at the end ofa` threading cut of predetermined length, and directional ram controlmechanism arranged to control the direction of feeding movement of saidram independently of the direction of rotation of said spindle during athreading operation, whereby a threading tool on said Alocking control mviding for direct 4. In a machine tool, a cuttercarrying ram arrangedfor axial feeding movement, a cutter spindle rotatably mounted in saidram, an electric motor operatively connected toy rotate said spindle andto feed said ram, means interconnecting said spindle and said ramfeeding means in manner to provide for establishing a predeterminedrelationship between the axial and the rotary movement of said spindlefor cutting threads, an electrically actuatedbrake associated with saidmotor,`and electrical tripmechanism operative to de-energize said motorand engage said brake when said ram arrives at a precisely predeterminedposition.

5. In` a machine tool-transmission and control mechanism for actuatingan operating machine element, an electric motor operatively connected toactuate said element, a normally open A manually controlled switchelectrically connected to energize said motor when closed, a holdingswitch operative to close in response. to closing of said manuallycontrolled switch and operative n to maintain said motor energized foreffecting continuous movement of said element, a limit switch operativein response to movement of said machine element to a predeterminedposition and functioning to stop said element by de-energizing saidmotor, and a selective conditioning switch operable to render saidholding switch inoperative, whereby said motor may be started andstopped by said` manually controlled switch to effect jogging movementof said machine element when said holding switch is inoperative.

6. In a machine tool, a base, a working element movably mounted on saidbase, electrically conM trolled driving mechanism operatively connectedto elect movement of raidv element relative to said base, a manuallyoperable switch arranged to eilect starting of said driving mechanism,interlocking control means arranged to eect continued movement ofY saidelement regardless of whether or not said manually operable switch isopened, a limit switch arranged to stop said driving mechanism uponarrival. of said'element ata predetermined position, and a selectivelyoperable switch a "ged to render said inters ineffective thereby4proswitch.

'7. Inv a machine tool including a base and a Work element movablerelative to said base, an electric motor operatively connected to effectmovement of said element relative to said base, a hr'alre associated witi said motor, limit switches operatively connected to effectde-energlzation of said motor and engagement of said brake at each endof the course of travel of said element, control means selectivelyoperable to render said brake inoperative, means associated with saidcontrol means and arranged to render one of said limit switchesinoperative when said brake is inoperative, and means responsive to theother of said limit switches and operative upon said brake control meansin manner to result in Ieffecting engagement of said brake whenever saidother limit switch is actuated.

8. In a machine tool having a spindle carrying support. a trainoperative to drive said support in feeding movement including adisconnecting clutch, trip mechanism arranged to disengage saidclutch'upon arrival of said support at a predetermined position,electrically controlled driv- "g and stopping of said v drivingmeclrianisrn o," said manually operable

